Generally, an electronic device, especially a portable terminal, means a device with which a user communicates with another user through a mobile communication base station while carrying it, or which provides a function to allow a user to access a service which is provided by a service vender. With the development of mobile communication technologies and an information and communication industry, a service field using a portable terminal has been rapidly expanded. For example, the early mobile communication services were limited to the calling of a counterpart, voice communication, short message transmission, etc. However, the services have been gradually expanded to multimedia services such as moving images, entertainment services such as games, banking services such as mobile banking, etc. and users of portable terminals have also gradually expanded from the youth to elderly people.
Recently, multimedia services provided through portable terminals have been strengthened, and portable terminals such as a smart phones or tablet PCs that come close to a conventional personal computer in function have been commercialized. Accordingly, an environment has been developed in which a person is capable of enjoying a moving image or the Internet and further conducting business using a smart phone or a tablet PC. In addition, as a display unit using a touch screen has been substituted for a keyboard constituted of physical switches as well as an output of a screen, it is capable of implementing an input simultaneously. Accordingly, although the portable terminal has been miniaturized, it can be provided with an expanded display unit.
On the other hand, with relation to the expansion of functions, various additional devices are utilized. For example, there are provided devices including an additional device with a simple structure such as a cradle providing a user with a convenience when a battery pack is charged in a state that the portable terminal is cradled, or when a user uses a multimedia function, and a docking station on which a portable terminal is mounted and which may be connected to an external audio or image device. In the case where an audio device is docked with the portable terminal, the audio device can reproduce files stored in a storage medium such as a compact disk (CD). A user can freely store desired files in the portable terminal compared with a storage medium for a general audio device. Therefore, if the user has a docking station equipped with a function of an audio device, it is possible to utilize various and abundant multimedia contents using the portable terminal.
Further, another additional device includes an input device which is separately provided to the portable terminal, particularly an input device which expands and is added to a keyboard. In the case of a smart phone or a tablet PC, it has a performance equal to or proximate to that of a home or office computer. Accordingly, it is possible to perform a simply task or web-surfing with the smart phone or the tablet PC. Furthermore, the smart phone or the tablet PC has an excellent mobility in comparison with a lap-top computer. In the case of such a smart phone or a tablet PC, a separate input device connectable to a portable terminal is implemented, thereby enhancing a convenience of a user. That is, if the user wants, he/she can substantially utilize the portable terminal, such as a tablet PC, like a lap-top computer through the input device anywhere.
When the portable terminal is coupled with the separate input device, the portable terminal is cradled on the input device at a desired angle. Accordingly, an input can be achieved through the input device. However, since the portable terminal is cradled, it is difficult to implement an input on a touch screen with an input member such as a stylus pen or an electronic pen. That is, because the touch screen has an unsuitable input angle to a hand grasping the electronic pen, there is an inconvenience in that the portable terminal is separated from the input device and put on a floor when an input is implemented with an electronic pen.
Moreover, in order to cradle the portable terminal, the input device has to be adjusted to balance of weight of the portable terminal. Therefore, since the input device has to include a metal material or a material with a constant weight, an unnecessary material as well as a material required to implement the input is provided and it causes to increase a material cost unnecessarily.